Drive system, especially for a motor vehicle

ABSTRACT

A drive system which has a drive unit with a drive shaft; a centrifugal mass arrangement, which is mounted on the drive shaft; and an electrical machine, comprising a stator arrangement and a rotor arrangement, where the rotor arrangement is mounted on the centrifugal mass arrangement, and where the stator arrangement and the rotor arrangement are adjacent to each other in the radial direction. So that optimum use can be made of the space available inside the drive unit, and so that the overall length of the drive unit required in the axial direction relative to the axis of rotation (A) can be kept as short as possible, the centrifugal mass arrangement has a contour such that, relative to the axis of rotation (A), a receiving space ( 71 ) is formed radially inside the electrical machine. The receiving space is bounded on at least one side by the centrifugal mass arrangement, and at least one additional component of the drive unit is installed in the receiving space.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention pertains to a drive system, especially fora motor vehicle, having a centrifugal mass mounted on a drive shaft andan electrical machine with a rotor mounted on the centrifugal mass and astator arranged radially with respect to the rotor.

[0003] 2. Description of the Related Art

[0004] Drive systems of this type can be designed in many different waysand usually have, first, a prime mover. A prime mover of the type inquestion can be, for example, a combustion machine such as an internalcombustion engine or the like. Drive systems of the known type alsousually have a drive unit, which can be built up in turn out of variouscomponents. For example, the drive unit can have a drive shaft, by meansof which the torque produced by the prime mover can be transmitted toother components. The drive unit can also include a centrifugal massarrangement, which is mounted on the drive shaft. The drive unit canalso have an electrical machine.

[0005] In general, these electrical machines can be rotating machines,for example, which use a magnetic field to convert electrical energyinto mechanical energy according to the motor principle or mechanicalenergy into electrical energy according to the generator principle.

[0006] These types of electrical machines, which can be designed eitheras synchronous machines or as asynchronous machines, usually have afirst machine component and a second machine component. The two machinecomponents rotate relative to each other or can be rotated relative toeach other. The two machine components are mounted adjacent to eachother in the radial direction. One of the two machine components isusually mounted radially inside the other machine component with respectto the axis of rotation of the electrical machine. Depending on thedesign of the electrical machine, one of the machine components can be arotor arrangement and the other machine component can be a statorarrangement. The stator arrangement, also called simply the stator, isusually the stationary part, whereas the rotor arrangement, also calledsimply the rotor, is the rotating part.

[0007] Depending on the design of the electrical machine, the statorcomponent consists, for example, of a sheet packet, which forms a yokeand a number of teeth. The electrical windings are laid in the groovesbetween the teeth. The magnetic field of the electrical machine isproduced when current passes through these windings. The rotorarrangement consists, for example, of a sheet packet, on which a numberof magnets, possibly permanent magnets, are mounted.

[0008] One of the areas in which electrical machines are used is that ofvehicles of all types. In vehicles, electrical machines are used intheir function as generators. When these electrical machines thusoperate according to the generator principle, they produce electricalenergy, which can then be made available to other consumers. In anotherapplication in vehicles, electrical machines are used asstarter-generators, for example. A starter-generator is an electricalmachine which is mounted between the drive shaft of a prime mover, suchas the crankshaft of an internal combustion engine, and a component ofthe drive unit, possibly a clutch, a gearbox, or the like, in the drivesystem of the vehicle. The starter-generator can be used, first, tostart the prime mover. Once the vehicle is in operation, it can alsooperate as a generator and can therefore replace both the starter andthe generator in the vehicle.

[0009] In addition to the components already described above, the driveunit can also include other components, which can include, for example,a clutch, a gearbox, a torque converter, etc.

[0010] A drive system of this type is described in, for example, DE 19927 261. These types of drive systems are used to advantage in motorvehicles. Especially in the vehicle sector, however, the need to reducethe amount of space required for the drive system is increasing. Thiscan be explained by advances in engineering, which make it necessary toaccommodate ever-increasing numbers of components in the enginecompartment of the vehicle. The solution disclosed in the publicationcited above already offers a way to reduce the space required toaccommodate the drive system.

SUMMARY OF THE INVENTION

[0011] Proceeding from the state of the art cited above, the object ofthe present invention is to improve the drive system of the typedescribed above so that the available space is utilized to the bestpossible degree and so that the axial length of the drive system can bekept as short as possible. In addition, an especially advantageous useof drive system of this type is to be presented.

[0012] The present invention is based on the insight that additionalspace, which can be used to accommodate components of the drive unit,can be created by designing the centrifugal mass arrangement in aspecial way.

[0013] According to the first aspect of the invention, the centrifugalmass arrangement has a contour such that a receiving space is formedradially inside the electrical machine; the receiving space is boundedon at least one side by the centrifugal mass arrangement; and at leastone additional component of the drive unit is accommodated in thereceiving space.

[0014] As a result of the drive system according to the invention, anadditional receiving space is created, in which additional components ofthe drive unit can be accommodated. According to the invention, theadditional receiving space is formed in the area of the electricalmachine. Giving the centrifugal mass arrangement a special contourcreates the additional receiving space.

[0015] The electrical machine has, first, a stator arrangement and arotor arrangement, which rotate relative to each other or which can berotated relative to each other. Depending on the design of theelectrical machine, either the rotor arrangement or the statorarrangement can be mounted radially inside the other arrangement withrespect to the axis of rotation of the electrical machine. When theelectrical machine is of the external rotor type, the stator arrangementis mounted radially inside the rotor. In the case of an electricalmachine of the internal rotor type, the rotor will be radially insidethe stator. The present invention is not limited to one specific type ofelectrical machine. Electrical machines of the external rotor type andthose of the internal rotor type can both offer advantages. Synchronousmachines, especially synchronous machines excited by permanent magnets,and asynchronous machines can be cited as examples of suitableelectrical machines.

[0016] The centrifugal mass arrangement according to the invention has acontour such that a receiving space is formed radially inside theelectrical machine, that is, radially inside the rotor arrangement orradially inside the stator arrangement. “Radially inside” is to beinterpreted again in relationship to the axis of rotation of theelectrical machine. When the electrical machine is installed in a drivesystem of the type described above, it is advantageous for the axis ofrotation of the electrical machine to be the same as the axis ofrotation of the drive shaft and the same as the axis of rotation ofother power takeoff shafts downline from the drive shaft.

[0017] Additional components of the drive unit can be accommodated inthe receiving space formed by the special design of the centrifugal massarrangement. Thus optimum use is made of the space available. At thesame time, the overall axial length of the drive unit and thus of theoverall drive system is further reduced. The axial orientation is againbased on the axis of rotation of the electrical machine or on thepreviously mentioned axis of rotation of the drive unit.

[0018] Thus the invention is not limited to specific types of componentsor to specific numbers of components, which can be mounted in thereceiving space. The type and number of components depend on the size,type, and area of application of the electrical machine and of the driveunit or drive system. A few nonexclusive examples of components, whichcan be installed advantageously in the receiving space, will bedescribed in greater detail below in the further course of thespecification.

[0019] According to the invention, the rotor arrangement is mounted onthe centrifugal mass arrangement. This has the effect of reducing therequired space, but it also has the effect of increasing the mass momentof inertia of the centrifugal mass arrangement.

[0020] So that axial misalignments which could occur as a result of, forexample, the powerful forces of the permanent magnets in the rotorarrangement can be prevented, it is advantageous for the stator and therotor to be connected to each other by suitable fastening means such asscrews, bolts, or the like until after they have been mounted in thedrive unit.

[0021] It is advantageous for the drive system to have a prime mover inwhich the electrical machine is installed axially between the primemover and the centrifugal mass arrangement. “Axially” is to beinterpreted here again in relationship to the axis of rotation of theelectrical machine or to the axis of rotation of the drive unit or ofthe drive system. As already explained above, it is advantageous forthese axes of rotation to be the same. In this type of design, theelectrical machine is mounted on the side of the prime mover that facesthe flywheel arrangement. As a result, a drive unit with an especiallycompact design can be achieved, and thus the design of the entire drivesystem becomes especially compact.

[0022] The invention is not limited to a specific type of prime mover.The prime mover can consist, for example, of a combustion machine suchas an internal combustion engine or the like.

[0023] It can be advantageous to install the drive unit in a one-part ormulti-part housing. If a multi-part housing is used, a spacer elementsuch as a spacer ring or the like can be provided between the individualparts of the housing. A spacer element of this type makes it possible tocompensate easily for any discrepancies in length that may be present.Thus the individual parts of the housing can be produced with apredetermined geometric contour, but it will still be possible toinstall the housing parts in different drive systems. Any lengthdiscrepancies that may be present can be easily and inexpensivelycorrected by the use of spacer elements of suitable size. It isconceivable, for example, that the spacer element could be designed asan independent structural component. It is also conceivable that thespacer element could be an integral part of one of the housing parts.

[0024] It can be advantageous to attach the stator arrangement to thehousing by the use of a stator bracket. The housing can be, for example,the bell of the centrifugal mass arrangement. It is also possible, ofcourse, for the stator bracket to be attached directly to the primemover.

[0025] In a further elaboration, it is possible for the stator bracketto have a cooling device. This cooling device can be used effectively tocool the individual components of the electrical machine, especially thestator arrangement. As will be explained in greater detail in thefurther course of the specification, the cooling device can also beused, if desired, to cool additional components or parts of additionalcomponents which are mounted in the receiving space according to theinvention.

[0026] If care is taken to mount the stator bracket appropriately on thehousing of the drive unit or directly on the prime mover, it is possiblefor the cooling device in the stator bracket to be connected to thecooling device of the prime mover, so that the stator bracket can becooled by the cooling device of the prime mover. In the case of aninternal combustion engine, this means that the bracket would be cooledby the engine cooling water or by motor oil.

[0027] It can be advantageous for the stator bracket to form one of theboundaries of the receiving space.

[0028] In a further elaboration, the centrifugal mass arrangement canhave two areas, which are arranged radially with respect to each other.“Radial” is based here on the axis of rotation of the centrifugal massarrangement, which is advantageously the same as the axis of rotation ofthe drive shaft on which the centrifugal mass arrangement is mounted.One of the two areas is thus farther inward in the radial direction withrespect to the axis of rotation than the other area.

[0029] It is also advantageous for the two areas mentioned to be offsetfrom each other in the axial direction. “Axial” here again is based onthe axis of rotation of the centrifugal mass arrangement. Thecentrifugal mass arrangement thus acquires a step-like design.

[0030] To achieve this, the two areas are connected to each other by athird connecting area.

[0031] It can advantageous for the centrifugal mass arrangement to bemade in the form of a “pot”, which extends around the electricalmachine. This pot is formed in particular by the connecting area and bythe area of the centrifugal mass arrangement that is situated radiallyfarther outward with respect to the axis of rotation. In this way, thecomponents of the electrical machine are also well protected at the sametime. It can be advantageous for the radially outer area and theconnecting area to form two sides of a protected space of this type. Athird side of the protected space can be formed by, for example, thehousing wall. Depending on the design of the housing of the drive unit,the fourth wall of the protected space can be formed either also by awall of the housing or by a wall of the prime mover.

[0032] As a further elaboration, the radially inner area of the flywheelarrangement and the connecting area can form two sides of the receivingspace.

[0033] In a different embodiment, the centrifugal mass arrangement canhave two areas which are connected to each other and which are orientedat an angle to each other. In this way, the centrifugal mass arrangementcan be produced in an especially simple and low-cost manner. It can beprovided that the flywheel arrangement is produced as a single piece. Itis also conceivable that the individual areas of the flywheelarrangement are first produced separately and then connected to eachother.

[0034] It is advantageous in this case for the two areas of the flywheelarrangement to be oriented at an angle to each other. The invention isnot limited to specific angles, however. For example, the two areas canbe oriented at an angle of 90° to each other. In this case, thecentrifugal mass arrangement has an approximately L-shaped contour.Other angles and thus also other contours of the centrifugal massarrangement are also possible, of course, so that the invention is notlimited to the examples cited.

[0035] It can be advantageous for a first area of the centrifugal massarrangement to be designed as an attachment area for the attachment ofthe centrifugal mass arrangement to the drive shaft. A second area ofthe centrifugal mass arrangement can then be designed as a receivingarea for the rotor arrangement. In certain special cases, furthermore,it can advantageous for this second area of the centrifugal massarrangement to have at least one through-opening. Such through-openingsare especially helpful when components, which must extend at leastpartially out of the receiving space, are mounted in the receivingspace. Several nonexclusive examples of this will be explained ingreater detail in the further course of this specification.

[0036] It can be advantageous for the two areas of the centrifugal massarrangement to form two sides of the receiving space.

[0037] As already presented in the introduction to the specification,the drive unit can comprise many different components and assemblies.These can include, for example, a gearbox, a torque converter, etc. Thedrive unit can preferably also have a clutch. In this case, it ispreferable for at least one component of the clutch to be accommodatedin the receiving space.

[0038] The invention is not limited to specific types of clutches. Forexample, the clutch can be a friction clutch or some other type ofclutch.

[0039] If the drive system has a prime mover and a drive unit connectedto it, at least one component of the clutch in an embodiment of thistype will therefore be situated in front of the centrifugal massarrangement on the side facing the prime mover.

[0040] It is possible, for example, for at least one component of aclutch disk arrangement of the clutch to be accommodated in thereceiving space.

[0041] It is also conceivable that at least one component of anactuating device of the clutch could be accommodated in the receivingspace. The actuating device of the clutch can be designed in any desiredway. For example, the actuating device can be a hydraulic slavecylinder, a pneumatic actuator, or the like. Because of the specialdesign of the drive unit, it is advantageous for the actuating device tohave a concentric design. “Concentric” is based here on the axis ofrotation of the centrifugal mass arrangement or on the axis of rotationof the electrical machine.

[0042] If the actuating device of the clutch has an actuator, at leastsome of the components of the actuator can be advantageouslyaccommodated in the receiving space formed by the centrifugal massarrangement.

[0043] For example, the actuator can be designed so that it has acylinder. It can be advantageous in this case for the cylinder to beformed by the inside surface of the stator bracket described above. Inthis way, the stator bracket forms not only the appropriate areas of thecentrifugal mass arrangement but also one of the other sides of thereceiving space. A design of this type offers the advantage that theconventional cylinder normally required for the actuator can beeliminated. This leads, first, to cost savings in the production of theactuator. The design also leads to a further reduction in the amount ofspace required. Finally, the design makes it possible to cool theactuator in a very simple manner, because the actuator can be cooled bythe same system that cools the stator bracket.

[0044] It can be advantageous for the clutch to have a diaphragm spring.At least part of this diaphragm spring can be accommodated in thereceiving space.

[0045] Because one or more parts of the clutch can be installed in thereceiving space, the overall axial length of the drive unit and thus ofthe drive system becomes very short.

[0046] In another embodiment, at least one torsion damper can beaccommodated in the receiving space. It is especially advantageous touse the receiving space to hold a double arrangement or a multiplearrangement of torsion dampers. All the torsion dampers can, forexample, be connected by a set of external teeth to a large, internallytoothed sleeve or hub, which carries in turn a common cover ring. Thecreation of a receiving space according to the invention now makes iteasy to install two or more torsion dampers without increasing theamount of space required. This also leads to an especially goodisolation of the vibrations.

[0047] The centrifugal mass arrangement can be designed in manydifferent ways within the scope of the invention. The centrifugal massarrangement can be, for example, the flywheel of a clutch, possibly of afriction clutch. In another embodiment, the centrifugal mass arrangementcan be, for example, a torque converter, preferably its housing.

[0048] It is especially advantageous for the electrical machine to bedesigned as a starter-generator. A starter-generator of the type inquestion will be used increasingly in the future as a replacement forthe current combination of separate components, namely, a starter and agenerator. In comparison with past solutions, a starter-generator offersbetter efficiency, lower weight, and greater electrical power. In thefuture, energy consumers, which are driven mechanically today, will bedriven by electricity instead. A starter-generator can be used not onlyto start and to stop a prime mover, such as an internal combustionengine, but also to take over various other functions during theoperation of the engine such as braking functions, booster functions,battery management, active vibration damping, synchronization of theprime mover, etc.

[0049] As described above, the starter-generator can be mountedadvantageously in the same area as that occupied by the centrifugal massarrangement, such as a flywheel, or it can be integrated into thisarrangement; the starter-generator will therefore be safely protected ina housing. If, from the perspective of the prime mover, a clutch islocated behind the centrifugal mass arrangement, the starter-generatorwill also be inside the clutch bell, which usually surrounds a clutch.As a result of the special design of the centrifugal mass arrangement,i.e. the creation of an additional receiving space, an especiallyfavorable, compact arrangement of the individual components is found inthis area of the drive unit, which comprises, for example, a pressureplate arrangement of a clutch, a clutch disk arrangement, a clutchactuating device, and possibly an intermediate flywheel. Optimum use ismade of the space available to house these components, and the overallaxial length of the drive unit can be kept as short as possible.

[0050] According to a second aspect of the invention, a drive systemaccording to the invention as described above can be used to particularadvantage in a commercial vehicle (truck).

[0051] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconjunction with the accompanying drawings. It is to be understood,however, that the drawings are designed solely for purposes ofillustration and not as a definition of the limits of the invention, forwhich reference should be made to the appended claims. It should befurther understood that the drawings are not necessarily drawn to scaleand that, unless otherwise indicated, they are merely intended toconceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0052]FIG. 1 shows a longitudinal cross section through a firstembodiment of the drive system according to the invention;

[0053]FIG. 2 shows a longitudinal cross section through a secondembodiment of the drive system according to the invention

[0054]FIG. 3 shows a longitudinal cross section through a thirdembodiment of the drive system according to the invention; and

[0055]FIG. 4 shows a longitudinal cross section through a fourthembodiment of the drive system according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

[0056]FIG. 1 shows a drive system 10, which is designed in particularfor use in a motor vehicle, preferably in a commercial vehicle. Thedrive system 10 has a drive unit 18, which has a drive shaft 11. By wayof the drive shaft 11, which rotates around an axis of rotation A, thedrive unit 18 is connected to a prime mover (not shown). The prime movercan be, for example, a combustion machine such as an internal combustionengine or the like. The torque produced in the prime mover istransmitted via the drive shaft 11, which can be, for example, acrankshaft, to the adjacent assemblies of the drive unit 18.

[0057] The drive shaft 11 is also connected to a centrifugal massarrangement 70. The centrifugal mass arrangement 70 in the presentexample is the flywheel of a clutch 40, which, in the present example,is designed as a friction clutch.

[0058] The individual assemblies of the drive unit 18 are mounted in ahousing, which, in the present example, consists of several housingparts. A first housing part 12 is a flywheel bell. Another, secondhousing part 13 can be designed as a gearbox bell, for example, or thelike. Between the two housing parts 12, 13, a spacer element 14 in theform of a spacer ring is provided, which can be used during theinstallation of the drive unit 18 in a drive system 10 to compensate forany length discrepancies which may be present.

[0059] An electrical machine 30 is mounted inside the flywheel bell 12between the prime mover (not shown) and the flywheel 70. This machinefunctions as a starter-generator. The electrical machine 30 has a rotorarrangement 31 and a stator arrangement 32. The electrical machine 30 isof the external rotor type, which means that the rotor arrangement 31 islocated farther outward in the radial direction with respect to the axisof rotation A than the stator arrangement 32.

[0060] The rotor arrangement 31 is connected to the centrifugal massarrangement 70 by a suitable rotor fastening means 33 such as screws orbolts. In this way, the mass moment of inertia of the centrifugal massarrangement 70 is also increased. Radially inside of the rotorarrangement 31, the stator arrangement 32 is installed, which isconnected to the first housing part 12 by a stator bracket 34. Theconnection can be accomplished, for example, by means of suitable statorfastening means 36 such as screws or bolts. In the stator arrangement34, furthermore, a cooling device 35 is provided, which is connected forexample, to a cooling system of the prime mover (not shown). In thisway, the stator bracket 34 and thus also the stator arrangement 32 canbe cooled in a very simple and effective manner.

[0061] The clutch 40 in the present case is designed as a frictionclutch and is located inside a clutch housing 41, that is also referredto as “clutch bell”. The clutch housing 41 is connected to thecentrifugal mass arrangement 70 by appropriate fastening means 42 suchbolts or screws.

[0062] The clutch 40 also has a clutch pressure plate 43; in the presentexemplary embodiment, the opposing pressure plate is formed by thecentrifugal mass arrangement 70.

[0063] An actuating device 45 actuates the clutch pressure plate 43. Forthis purpose, the clutch pressure plate 43 is connected by a diaphragmspring 46 to the actuating device 45 in the manner known in and ofitself.

[0064] A clutch disk arrangement 44 is provided between the clutchpressure plate 43 and an area of the centrifugal mass arrangementopposite the pressure plate 43. A torsion damper 60 is also provided inthe clutch disk arrangement 44. The clutch disk arrangement 44 isconnected to the hub 16 of a power takeoff shaft 17. When the clutch 40is closed, the torque provided by the drive shaft 11 can be transmittedin the manner known in and of itself via the clutch disk arrangement 44to the power takeoff shaft 17.

[0065] To prevent axial misalignments of the stator arrangement 32 andthe rotor arrangement 31 until after they have been installed, thesecomponents can be held in place initially by appropriate fasteningmeans. For example, screws or bolts could connect the stator arrangement32 and the rotor arrangement 31 to each other until they are installed.Assembly fastening means 37 such as bolts or screws can also connect thestator arrangement 32 to the centrifugal mass arrangement 70. It isadvantageous to remove the fastening means as soon as the electricalmachine 30 has been installed in the drive system and adjusted.

[0066] So that the space required for the drive unit 18 and thus for theentire drive system 10 can be kept as small as possible, it is necessaryto create as much room as possible to accommodate the individualcomponents of the drive unit 18, i.e., of the individual assemblies ofthe drive unit 18. In the present exemplary embodiment, designing thecentrifugal mass arrangement 70 in a special way creates additionalroom.

[0067] The centrifugal mass arrangement 70 according to FIG. 1 consists,in all, of three areas, i.e., a first area 72, a second area 73, and athird area 74, which connects the other two areas 72 and 73. The designof the centrifugal mass arrangement 70 is selected so that the firstarea 72 serves initially as the attachment area. The centrifugal massarrangement 70 is thus connected to the drive shaft 11 by thisattachment area 72. This can be accomplished by means of suitablefastening means 15 such as bolts or screws. Radially outside theattachment area 72 with respect to the axis of rotation there is thesecond area 73 of the centrifugal mass arrangement 70, which, in thepresent case, serves as the receiving area for the rotor arrangement 31.This receiving area 73 also serves as the opposing pressure plate forthe pressure plate 43 of the clutch.

[0068] The two areas 72 and 73 are also offset from each other in theaxial direction. The axial offset is again to be understood withreference to the axis of rotation A. In this way, the centrifugal massarrangement 70 has a step-like contour, the height of the step beingdetermined by the length of the connecting area 74.

[0069] Through the cooperation between the connecting area 74 and thesecond area 73, the centrifugal mass arrangement 70 designed in this wayforms a kind of pot, which surrounds the electrical machine 30. Theconnecting area 74 and the second area 73 form two sides of a protectedspace for the electrical machine 30. The third and fourth sides of thisprotected space are formed in the present example by two sides of thehousing part 12. The electrical machine is thus reliably protected fromdamage and dirt in the drive unit 18.

[0070] As a result of the special design of the centrifugal massarrangement 70, furthermore, a receiving space 71 is created, in whichadditional components of the drive unit 18 can be accommodated. In thepresent example, the receiving space 71 is bounded on two sides by thecentrifugal mass arrangement 70, namely, by the first area 72 and by theconnecting area 74. With respect to the axis of rotation A, thereceiving space 71 is located radially inside the electrical machine 30;and in the exemplary embodiment according to FIG. 1, at least onecomponent of the clutch 40, among other things, is accommodated in thisspace. In the present example, parts of the clutch disk arrangement 44and the torsion damper 60 are located in the receiving space 71.

[0071] As a result of the special design of the centrifugal massarrangement 70, another space for holding components is created radiallyinside the electrical machine 30, so that optimum use can be made of theavailable space and the overall axial length (based on the axis ofrotation A) of the drive unit 18 and thus of the overall drive system 10can be kept as short as possible.

[0072]FIG. 2 shows a drive unit 18 of a drive system 10, which issimilar in its basic design to the drive unit 18 of FIG. 1. With respectto the structure and the function of the drive unit 18, reference cantherefore be made initially to the explanations offered in associationwith FIG. 1. The same components have been provided with the samereference numbers.

[0073] The drive unit 18 according to FIG. 2 has a receiving space 71which is bounded on two sides by the first area 72 and the connectingarea 74 of the centrifugal mass arrangement 70; with respect to the axisof rotation A and the electrical machine 30, this space is situatedradially inside the machine, and a double arrangement of torsion dampers60, 61 is provided in it. Of course, it is also conceivable that morethan two torsion dampers could be provided in the receiving space 71.All torsion dampers 60, 61 are connected to the hub 16. For example, thetorsion dampers 60, 61 can be connected by a set of external teeth to alarge, internally toothed sleeve, which carries a common cover ring.

[0074] The installation of two or more torsion dampers 60, 61 makes itpossible to provide especially good isolation of the vibrations.

[0075]FIGS. 3 and 4 show exemplary embodiments of a drive unit 18 for adrive system 10 which have the same assemblies as in the embodimentsaccording to FIGS. 1 and 2, but in which the assemblies have beendesigned and installed differently.

[0076] The drive unit 18 again has a multi-part housing, which, as inFIGS. 1 and 2, can consist of a first housing part 12 and a secondhousing part 13. In contrast to the examples according to FIGS. 1 and 2,a separate spacer element is not provided in the exemplary embodimentsaccording to FIGS. 3 and 4. As an alternative, it would also be possiblefor the spacer element to be permanently integrated into one of the twohousing parts 12 or 13.

[0077] The drive unit 18 also has a centrifugal mass arrangement 70,except that here its contour differs from that shown in FIGS. 1 and 2.According to FIGS. 3 and 4, the centrifugal mass arrangement 70 consistsof two areas 72′, 73′, which are connected to each other and which areoriented at an angle to each other. In the present exemplary embodiment,the centrifugal mass arrangement 70 is designed as a single piece. It isalso conceivable, however, that the two areas 72′, 73′ of thecentrifugal mass arrangement 70 could be produced separately first andthen joined to each other to form the flywheel. This centrifugal massarrangement 70 is connected via the first area 72′ to the drive shaft11, which can be accomplished again by means of appropriate screws orbolts or the like. The drive shaft 11 rotates around an axis of rotationA, as also in FIGS. 1 and 2.

[0078] The second area 73′ of the centrifugal mass arrangement 70projects from the first area 72′ at a certain angle. In the examplesaccording to FIGS. 3 and 4, this angle is approximately 90°, so that thecentrifugal mass arrangement 70 acquires the approximate shape of an“L”.

[0079] As also in FIGS. 1 and 2, an electrical machine 30 in theexemplary embodiments according to FIGS. 3 and 4 is designed as astarter-generator and is installed between a prime mover (not shown) andthe centrifugal mass arrangement 70. The electrical machine 30 islocated inside the first housing part 12. The rotor arrangement 31 ofthe electrical machine 30 is attached to the centrifugal massarrangement 70, i.e., to the second area 73′ of the centrifugal massarrangement 70, by suitable rotor fastening means 33. The second area73′ can thus be referred to as a “receiving area”. In contrast, thefirst area 72′ of the centrifugal mass arrangement 70 can be referred toas an “attachment area”.

[0080] The stator arrangement 32 is attached by a stator bracket 34 tothe first housing part 12. This can again be done by the use of suitablestator fastening means 36. Inside the stator bracket, a cooling device35 is provided, by means of which at least the stator arrangement 32 canbe cooled. The cooling device 35 can be connected to, for example, acooling device of the prime mover (not shown).

[0081] As seen from the perspective of the electrical machine 30, aclutch 40 is provided behind the centrifugal mass arrangement 70. Theclutch 40 has, first, two clutch pressure plates 43, 43′; the clutchpressure plate 43′ is connected to the second area 73′ of thecentrifugal mass arrangement 70 by suitable fastening means such asscrews or bolts.

[0082] The clutch 40 has a clutch disk arrangement 44, which isconnected to the hub 16 of a power takeoff shaft. A torsion damper 60 isalso integrated into the clutch disk arrangement 44.

[0083] As also in the exemplary embodiments according to FIGS. 1 and 2,the centrifugal mass arrangement 70 is also designed in the exemplaryembodiments according to FIGS. 3 and 4 in such a way that it creates areceiving space 71 radially inside the electrical machine 30, thisreceiving space 71 being bounded on at least one side by the centrifugalmass arrangement 70. According to the examples of FIGS. 3 and 4, thereceiving space 71 is bounded on two sides by the centrifugal massarrangement 70 via the two areas 72′, 73′ of the centrifugal massarrangement 70. A third side of the receiving space 71 is bounded by thestator bracket 34.

[0084] Certain components of the clutch 40 are installed inside thereceiving space 71 and thus in front of the centrifugal mass arrangement70. First, the actuating device 45 of the clutch is mounted in thereceiving space 71. This actuating device 45 consists of an actuator 47mounted in a cylinder 48. The actuator 47 actuates a diaphragm spring46, at least part of which is also located in the receiving space 71.The diaphragm spring 46 is therefore situated in front of thecentrifugal mass arrangement 70, on the side facing the prime mover. Theactuator 47 can be, for example, a concentric pneumatic actuator.

[0085] Because of the way in which the drive unit 18 is designed, thesize of the drive unit 18 can be made very small in the axial direction(relative to the axis of rotation A).

[0086] So that the clutch pressure plate 43 can be actuated properly,through-openings 75, 76 are provided in the second area 73′ of thecentrifugal mass arrangement 70, through which openings the diaphragmspring 46 can make contact with the clutch pressure plate 43. Theactuating device 45 can thus perform its function properly via thediaphragm spring 46.

[0087]FIG. 4, finally, shows an embodiment of a drive unit 18 for adrive system 10, which is approximately the same as that according toFIG. 3. For this reason, reference can be made initially to theexplanations of the basic design and function offered in regard to FIG.3. The same components are again provided with the same referencenumbers.

[0088] The embodiment according to FIG. 4 differs from the designvariant shown in FIG. 3 in that the actuating device 45, comprising anactuator 47, no longer has its own independent cylinder 48. Instead, thecylinder 48 is formed by the surface 38 of the stator bracket 34 whichis on the inside, as seen from the perspective of the axis of rotationA. The inside surface 38 of the stator bracket 34 thus servessimultaneously as the cylinder for the actuator 47, which can be, forexample, a concentric, pneumatic actuator.

[0089] In comparison with the design variant shown in FIG. 3, thecylinder of the actuator 47 is eliminated in the embodiment according toFIG. 4. This leads among other things to a further reduction in theamount of space required. In addition, the actuator 47 can be easilycooled efficiently, because it can be cooled simultaneously by thecooling device 35 that cools the stator bracket 34.

[0090] The goal achieved by the present invention is that optimum usecan be made of the space available inside the drive unit 18, so that theoverall axial length of the drive unit 18 in relationship to the axis ofrotation A can be kept as short as possible.

[0091] Thus, while there have shown and described and pointed outfundamental novel features of the invention as applied to a preferredembodiment thereof, it will be understood that various omissions andsubstitutions and changes in the form and details of the devicesillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit of the invention. For example, itis expressly intended that all combinations of those elements and/ormethod steps which perform substantially the same function insubstantially the same way to achieve the same results are within thescope of the invention. Moreover, it should be recognized thatstructures and/or elements and/or method steps shown and/or described inconnection with any disclosed form or embodiment of the invention may beincorporated in any other disclosed or described or suggested form orembodiment as a general matter of design choice. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

What is claimed is:
 1. A drive system for a motor vehicle, said drivesystem comprising: a drive shaft; a centrifugal mass mounted on saiddrive shaft for rotation about an axis and being profiled with an axialreceiving space; an electrical machine comprising a rotor mounted on thecentrifugal mass and a stator arranged radially with respect to saidrotor; and at least one component accommodated in said receiving space.2. A drive system as in claim 1 wherein said electrical machine ismounted on a side of said centrifugal mass which is mounted to saiddrive shaft.
 3. A drive system as in claim 1 further comprising ahousing having at least one part, said centrifugal mass and saidelectrical machine being arranged in said housing.
 4. A drive system asin claim 3 further comprising a stator bracket which attaches saidstator to said housing.
 5. A drive system has in claim 4 furthercomprising a cooling channel in said stator bracket.
 6. A drive systemas in claim 4 wherein said stator bracket bounds said receiving spaceradially.
 7. A drive system as in claim 1 wherein said centrifugal masscomprises a radially inner first area, a radially outer second area, anda third area connecting said first and second areas, which are offsetboth radially and axially.
 8. A drive system as in claim 7 wherein saidfirst area and said third area bound two sides of said receiving space.9. A drive system as in claim 1 wherein said centrifugal mass comprisesa first area and a second area which are connected to each other at anangle.
 10. A drive system as in claim 9 wherein said first areacomprises an attachment area for attaching said centrifugal mass to saiddrive shaft, and said second area comprises an attachment area forattaching said rotor, said second area having at least one throughopening.
 11. A drive system as in claim 9 wherein said first and secondareas bound two sides of said receiving space.
 12. A drive system as inclaim 1 further comprising a clutch, said clutch comprising saidcomponent accommodated in said receiving space.
 13. A drive system as inclaim 12 wherein said clutch comprises a clutch disk arrangement, saidclutch disk arrangement comprising said component in said receivingspace.
 14. A drive system as in claim 12 wherein said clutch comprisesan actuating device, said actuating device comprising said componentaccommodated in said receiving space.
 15. A drive system as in claim 14wherein said actuating device comprises an actuator, said actuatorcomprising said component accommodated in said receiving space.
 16. Adrive system as in claim 15 further comprising a housing having at leastone part, said centrifugal mass and said electrical machine beingarranged in said housing, and a stator bracket attaching said stator tosaid housing, said stator bracket having an inner surface, said actuatorcomprising a cylinder formed by said inner surface.
 17. A drive systemas in claim 12 wherein said clutch comprises a diaphragm spring which isaccommodated in said receiving space.
 18. A drive system as in claim 1wherein said at least one component comprises at least one torsiondamper.
 19. A drive system as in claim 1 wherein said electrical machineis a starter-generator.